U.S. patent number 7,472,522 [Application Number 11/655,659] was granted by the patent office on 2009-01-06 for protective rebar cover.
This patent grant is currently assigned to Mutual Industries North, Inc.. Invention is credited to Yongjian Yang.
United States Patent |
7,472,522 |
Yang |
January 6, 2009 |
Protective rebar cover
Abstract
Briefly, this invention comprises a rebar protective cover for
use on the projecting free end of a concrete reinforcing bar to
prevent impact injuries comprising: (a) a hollow cylindrical
collar, having an open end and a closed end, (b) an overhanging
impact head of substantial extent projecting laterally outwardly
beyond the closed end of said collar, (c) a bowl-shaped shaping
member having the concave surface facing the open end of the
collar, (d) a solid cementitious member occupying the space between
said closed end of the collar and the underside of said shaping
member, said cementitious member having a surface abutting the
underside of said shaping member complementary to said shaping
member and adapted to resist impact penetration, said protective
cover preventing penetration of the cover by rebar.
Inventors: |
Yang; Yongjian (Nanjing,
CN) |
Assignee: |
Mutual Industries North, Inc.
(Philadelphia, PA)
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Family
ID: |
39616700 |
Appl.
No.: |
11/655,659 |
Filed: |
January 17, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080168726 A1 |
Jul 17, 2008 |
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Current U.S.
Class: |
52/301; 52/244;
248/523; 138/96R |
Current CPC
Class: |
E04C
5/161 (20130101); E04C 5/20 (20130101); E04G
21/3252 (20130101); E04F 15/02488 (20130101); E04G
21/32 (20130101) |
Current International
Class: |
E04H
12/00 (20060101); B65D 59/00 (20060101); F16M
13/00 (20060101) |
Field of
Search: |
;52/301,300,689,244
;248/523 ;138/96R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-331028 |
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Feb 1998 |
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JP |
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WO 91/14839 |
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Oct 1991 |
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WO |
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Other References
US. Appl. No. 09/569,826, Dunn. cited by other .
J.A. Brydson, "Plastic Materials", 7th Edition,
Butterworth-Heinemann (pubs.), Oxford, England, (1999), pp.
205-246. cited by other .
Don Decristo Concrete Accessories, Catalog, p. 43. cited by other
.
Deslauriers, "Impalement-Protection Saftey Cap DISC System",
promotional flyer, Jun. 12, 1996. cited by other .
American Allsafe Company, "The Changing of the Guard", promotional
flyer. cited by other .
Mutual Industries, Inc., "Rebar Safety Products", Catalog, p. 39.
cited by other.
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Primary Examiner: Chilcot, Jr.; Richard E
Assistant Examiner: Triggs; Andrew J
Attorney, Agent or Firm: Mueth; Joseph E.
Claims
What is claimed is:
1. A rebar safety protective cover for use on the projecting free
end of a concrete reinforcing bar to prevent impact injuries
comprising: (a) a hollow cylindrical collar, having an open end and
a closed end, (b) an overhanging impact head of substantial extent
projecting laterally outwardly beyond the closed end of said
collar, (c) a bowl-shaped shaping member having the concave surface
facing the open end of the collar, said shaping member comprising a
plastic material, (d) a solid cementitious member occupying the
space between said closed end of the collar and the underside of
said shaping member, said cementitious member having a surface
abutting the underside of said shaping member complementary to said
shaping member and adapted to resist impact penetration, said
cementitious member preventing penetration of the cover by
rebar.
2. The rebar safety protective cover of claim 1 wherein the
cementitious member comprises cement, carborundum and ceramic
particles.
3. The rebar safety protective cover of claim 1 wherein said
plastic material includes a mixture of polyethlenes, one having a
density of about 0.945 and another of about 0.97.
4. The rebar safety protective cover of claim 3 wherein the first
mentioned polyethylene is present at about 95 weight percentage and
the another at about 5 weight percent.
5. The rebar safety protective cover of claim 1 wherein the plastic
material includes a mixture of polyethylenes, one having a
molecular weight in the range from about 2.5.times.10.sup.5 to
about 15.times.10.sup.5 and another a molecular weight in the range
above about 15.times.10.sup.5.
6. The rebar safety protective cover of claim 5 wherein said first
mentioned polyethylene has a density of about 0.945 and the another
polyethylene a density of about 0.97.
7. The rebar safety protective cover of claim 6 wherein the first
mentioned polyethylene is present in a weight amount of about 95%
and the another polyethylene in a weight about of about 5%.
8. The rebar safety protective cover of claim 1 wherein said impact
head has a flat outer surface for receiving impact.
9. The rebar safety protective cover of claim 1 wherein said
plastic material comprises a polyefin.
10. In combination, a rebar used to reinforce concrete wherein the
rebar has an exposed free end, and a safety protective cover
disposed on said exposed free end, said protective cover
comprising: (a) a hollow cylindrical collar, having an open end and
a closed end, (b) a flat overhanging impact head of substantial
extent projecting laterally outwardly beyond the closed end of the
collar, (c) a bowl-shaped shaping member having the concave surface
facing the open end of the collar, said shaping member comprising a
plastic material, (d) a solid cementitious member occupying the
space between said closed end of the collar and the underside of
said shaping member, said cementitious member having a surface
abutting the underside of said shaping member complementary to said
shaping member and adapted to resist impact penetration, said
cementitious member preventing penetration of the cover by
rebar.
11. The combination of claim 10 wherein the cementitious member
comprises cement, carborundum and ceramic particles.
12. The combination of claim 10 wherein said plastic material
includes a mixture of polyethylenes, one having a density of about
0.945 and another of about 0.97.
13. The combination of claim 12 wherein the first mentioned
polyethylene is present at about 95 weight percentage and the
another at about 5 weight percent.
14. The combination of claim 10 wherein the plastic material
includes a mixture of polyethylene, one having a molecular weight
in the range from about 2.5.times.10.sup.5 to about
15.times.10.sup.5 and another a molecular weight in the range above
about 15.times.10.sup.5.
15. The combination of claim 14 wherein said first mentioned
polyethylene is present in a weight amount of about 95% and the
another polyethylene in a weight about of about 5%.
16. The combination of claim 13 wherein the first mentioned
polyethylene has a density of about 0.945 and the another
polyethylene a density of about 0.97.
17. The combination of claim 10 wherein said impact head has a flat
outer surface for receiving impact.
18. The combination of claim 10 wherein said plastic material
comprises a polyefin.
Description
FIELD OF INVENTION
This invention relates to protective covers for exposed steel
reinforcing bars used in reinforced concrete.
BACKGROUND OF INVENTION
Steel reinforcing bars ("rebar") are used in reinforced concrete in
building structures. During the construction of buildings, the ends
of the rebar are often exposed and extend upwardly from recently
poured concrete sections or walls. Exposed ends are sharp and
present a hazard to workmen, particularly to workmen working
overhead. Many workmen have sustained puncture injuries, and in a
significant number of cases have been killed, due to accidentally
falling or stepping onto the exposed ends of the rebar.
Various protective safety covers have been proposed and used to
protect workmen from this hazard. Bush U.S. Pat. No. 4,202,378 and
Bush Design Pat. No. 262,093 refer to a protective safety cover for
use on the free projecting ends of rebar comprising a hollow
cylindrical body of a deformable plastic material, the body being
closed at one end and open at the other. A plurality of inwardly
extending projections are formed within the open end of the
cylindrical body to secure the protective cover to the rebar. The
closed end of the body has a flat circular head which extends
radially outwardly from the body to present an enlarged flat impact
surface. Other plastic protective covers for rebar are discussed in
Schimmelpfenning U.S. Pat. No. 5,884,443 and Don De Cristo Concrete
Accessories Inc. Catalog "Plastic Rebar Guard", p. 43. Lunn U.S.
Pat. No. 4,833,850 proposed a protective cover for rebar in the
form of a metal support adapted to hold a impact absorbing
spherical cushion.
When it was realized that these all plastic protective covers were
subject to penetration upon severe impact, such as a workman
falling from a height, it was proposed to insert a separate piece
of rebar through lateral holes near the closed end of the
cylindrical body to provide for a steel stop as discussed in
WO91/14839 and Underwood U.S. Pat. No. 5,363,618. This approach is
not self-contained, is inconvenient, and subject to not being
consistently practiced.
Consequently, protective covers having a built in metal plate or
"seat" in the bottom of the closed end of the body were developed.
Protective covers of this type are discussed in Schnepf U.S. Pat.
No. 5,313,757, Workman U.S. Pat. Nos. 5,447,290 and 5,613,336,
Deslauriers Impalement Protective "Safety Cap DISC System", Buffalo
American Allsafe Company "BarGard", Mutual Industries Inc. OSHA
Rebar Cups Part Numbers 14640-4 and 14640-5, Dunn U.S. Design Pat.
No. 408,268, and Kassardjian et al U.S. Pat. Nos. 5,381,636,
5,523,043, 5,568,708, 5,824,253, 5,943,836, 5,946,871 and Design
No. 363,657. Protective covers with metal plates or seats passed
the original Cal OSHA drop test.
However, after an investigation of job site injuries, Cal OSHA
subsequently declared that the existing protective covers with
metal plate or seat were inadequate, primarily due to being subject
to penetration through the side of the cylindrical body upon impact
on the head, resulting in serious puncture injuries to workmen
falling onto the rebar.
Cal OSHA since established a new and more stringent drop test which
all new rebar protective covers are required to meet. Kassardjian
et al U.S. Pat. No. 5,729,941 relates to a rebar cover having a
preformed metal stamping in the form of a bowl-shaped metal seat
which is incorporated in the closed inner end of the cylindrical
body. The bowl-shaped metal seat is said to be of a composition and
thickness to prevent penetration of the rebar through the seat and
thereby preclude penetration of the rebar through the side of the
cover body upon impact.
The use of a preformed bowl-shaped metal stamping as the seat adds
to the expense of the rebar protective cover.
Subsequently, a rebar protective cover having a hollow cylindrical
body and impact head of a thickness and integrally formed of a
plastic material was developed which was found to provide a
protective cover which passes the current Cal OSHA drop test. This
rebar protective cover is disclosed in applicant's co-pending U.S.
patent application Ser. No. 09/569,826, filed May 12, 2000, the
disclosure of which is incorporated herein by reference.
SUMMARY OF THE INVENTION
Briefly, this invention comprises a rebar protective cover for use
on the projecting free end of a concrete reinforcing bar to prevent
impact injuries comprising: (a) a hollow cylindrical collar, having
an open end and a closed end, (b) an overhanging impact head of
substantial extent projecting laterally outwardly beyond the closed
end of said collar, (c) a bowl-shaped shaping member having the
concave surface facing the open end of the collar, (d) a solid
cementitious member occupying the space between said closed end of
the collar and the underside of said shaping member, said
cementitious member having a surface abutting the underside of said
shaping member complementary to said shaping member and adapted to
resist impact penetration, said protective cover preventing
penetration of the cover by rebar when the cover is subjected to
the Cal OSHA drop test.
The invention further comprises the combination of a rebar used to
reinforce concrete wherein the rebar has an exposed free end and a
safety protective cover disposed on said exposed, said protective
cover comprising: (a) a hollow cylindrical collar, having an open
end and a closed end, (b) a flat overhanging impact head of
substantial extent projecting laterally outwardly beyond the closed
end of the collar, (c) a bowl-shaped shaping member having the
concave surface facing the open end of the collar, (d) a solid
cementitious member occupying the space between said closed end of
the collar and the underside of said shaping member, said
cementitious member having a surface abutting the underside of said
shaping member complementary to said shaping member and adapted to
resist impact penetration. said protective cover preventing
penetration of the cover by rebar when the cover is subjected to
the Cal OSHA drop test.
DESCRIPTION OF PREFERRED EMBODIMENTS
Turning to the drawings:
FIG. 1 is an exploded perspective view of the plastic parts of the
protective cover of this invention.
FIG. 2 is a sectional view of the assembled protective cover of
this invention.
FIG. 3 is a sectional, exploded view taken vertically through the
parts shown in FIG. 2, but taken prior to assembly with the cement
still in the unhardened state.
FIG. 4 is a side view of the assembled protective cover of this
invention when in place over a rebar.
FIG. 5 is a side view in partial breakaway of the assembled
protective cover of FIG. 2 positioned over rebar.
FIG. 6 shows the positioning of the assembled protective cover on
the rebar at the maximum possible angle, as required by the current
Cal OSHA drop test. The free end of the rebar abuts the inside of
the shaping member which is separated from the closed end of the
cylindrical body portion by cementitious member.
FIG. 7 is similar to FIG. 2 with the addition of the dimensions in
one preferred embodiment.
FIG. 8 shows three perspective views of the complete rebar
protective cover of this invention.
The hollow cylindrical collar 2 is closed at one end 6 and is open
at the other 7. The flat impact head 1 is formed so that when
joined to the cylindrical collar 2, the impact head extends beyond
and overhangs the collar 2.
The separately formed impact head 1 as shown is preferably circular
and has an area of about 16 square inches as required by Cal OSHA.
The impact head can also be square.
Four web-like buttresses 8, spaced at a 90.degree. interval, help
support the periphery of the impact head 1 around its
underside.
The fin holder 5 has the inside flanges 9 serve to keep the
protective cover longitudinally aligned with the rebar 10 by
gripping the sides of the rebar.
The fin holder 5, the shaping member 4, the collar 2 and the impact
head 1 are first individually formed by injection molding of the
polyolefins described herein.
Then the putty-like cement is poured into the collar 2 in an amount
sufficient so that when the shaping member 4 is inserted, the
cement rises to about mid-level inside the collar 2 as shown in
FIG. 2. The collar walls 11 are preferably thickened in this area.
The shaping member 4 itself is not capable of absorbing high impact
and serves to shape the surface of the cementitious material 3 to a
bowl shape as the concrete hardens. This concrete bowl shaped
surface abutting the underside of shaping member 4 acts as the high
impact absorbing seat.
The fin holder 5 is then placed in the collar 2 and the impact head
1 positioned against the closed end 6 of the collar 2. The assembly
is heated to cause the fin holder 5 to adhere to the inside of the
collar 2 and the impact head 1 to adhere to the closed end 6 of the
collar 2. This assembly can be performed before or after the cement
3 has hardened. Complete hardening of the cementitious material 3
takes about 24 hours. The shaping member 4 becomes adhered to the
surface of the hardened cement 3.
In the completed protective cover, the shaping member 4 is
preferably positioned such that the top of the shaping member is
about midway between the closed end 6 of the collar 2 and open end
of the collar and the concave bottom surface of the shaping member
4 is about one third the distance from the closed end 6 of the
collar to the open end of the collar 2. A preferred example of
these dimensions is shown in FIG. 7.
The plastic parts of the protective cover of this invention are
integrally molded, in standard plastic injection molding equipment,
using a high molecular weight polyolefin polymers. The plastic can
contain a small amount (about 0.04%) of an orange colorant such as
anti-UV red, a small amount of orange pigment (about 0.032%) and a
small amount of filler such as calcium chloride (about 1% to 3%),
all based on the total weight of polymers. These additives are
desirable, but not essential.
In my preferred embodiment, the plastic parts of the protective
cover are injection molded of a homogenous mixture of two very high
molecular weight polyethylene polymers as follows:
TABLE-US-00001 Molecular Weight Density Percentage Polymer
Distribution gTcm.sup.3 By Weight Extra High about 2.5 .times.
10.sup.5 to about 0.945 about 95% Molecular about 15 .times.
10.sup.5 Weight High Density Polyethylene Ultra High essentially
all about 0.97 about 5% Molecular over about Weight High 15 .times.
10.sup.5 Density Polyethylene
The upper limit of the molecular weight of the ultra high molecular
weight high density polyethylene is not critical. Such polymers
currently available are believed to be only slightly above
15.times.10.sup.5 but could be higher such as 20 or
25.times.10.sup.5.
The two polymers are premixed and colorant, pigment and filler are
added. A homogenous blend forms in the molten state which is then
injected into the cavity of the mold. Injection molding equipment
is used to form the protective cover to the desired shape.
The cementitious portion of the protective cover is a high strength
concrete mixed with carborundum/ceramic grain.
The cementitious portion 3 of the protective cover is prepared by
mixing:
TABLE-US-00002 Carborundum: 70%-80% Cement: 29%-19% and Ceramic
powder or quartzite: 1%
These ingredients are mixed with water. Various well known cement
additives can also be added in minor amounts. Those skilled in the
art can modify the ingredients and proportions.
The following are preferred ingredients:
1. The carborundum particles size: about 8-20 mesh
2. The quartzite particles size: about 40-50 mesh
3. Ceramic powder: composition is Al.sub.2O.sub.3, SIO.sub.2 and
MgO
4. Ceramic powder particle size: 40-50 mesh.
The upper surface of the impact head 1 of the protective cover is
preferably flat as shown in the Figures. However, a domed or
mushroom shaped upper surface is also acceptable.
The original Cal OSHA drop test required the protective cover be
capable of withstanding at least the impact of a 250 pound weight
dropped from a height of 10 feet without penetration failure of the
cover. This drop test was based on the rebar being aligned with the
longitudinal dimension of the cylindrical body portion.
The problem is that many prior protective covers in actual use,
upon impact, allowed the rebar to penetrate and pierce the side of
the cylindrical body at or around its junction with the impact
head. Failures of this kind have resulted in serious industrial
accidents.
Since it was found upon severe impact that the interior flanges 9
would break or give way, allowing the protective cover to become
cocked at an angle to the rebar, the latest Cal OSHA drop test
requires that it be conducted with the protective cover positioned
over the rebar as shown in FIG. 6.
The following test results demonstrated the efficacy of the rebar
safety protective cover of this invention.
A rebar protective cover was assembled using as the cementitious
material a mixture of carborundum about 75%, cement about 24% and
quartzite about 1%, all of weight.
Cal OSHA DROP TEST
Test Procedure:
The drop test was conducted in accordance with the latest Cal OSHA
procedure. The rebar protective cover of FIG. 7 was attached to the
sheared end of a 6 inch long #4 rebar mounted on a support. The
rebar was rigidly held in a vertical position during impact. A test
weight was suspended above the test item at the specified drop
height of 10 feet, as measured from the bottom of the test weight
to the top of the test item. The test weight consisted of 250
pounds of dry sand in a Kevlar bag having a circumference of 41
inches. The test weight was slowly raised to the specified drop
height. When the test weight reached the specified drop height, the
test weight was quickly released by cutting the support wire cable.
The test weight then impacted the test item. The test rebar
protective cover was then visually inspected for evidence of
physical damage. Three (3) drops were conducted: The first drop was
conducted with the plastic rebar protective cover of this invention
installed squarely on the rebar so that the impact head 1 is at a
right angle to the lengthwise dimension of the exposed rebar. The
second and third drops were performed with the plastic stabilizer
flanges 9 removed from the rebar protective cover of this invention
prior to the test. This allowed the rebar protective cover to sit
on the rebar with the impact head, at maximum angle out of level
(out of square). A drawing of this set-up may be seen in FIG. 6.
The free end of the rebar abutted the inside of the shaping member
4 at its lateral extremity, as shown.
Test Data:
TABLE-US-00003 Test Weight: 250 pounds Drop Height: 10 feet
Test Results:
The rebar caps completed the drop tests with no evidence of
cracking and/or splitting of the cementitious material.
As used herein, the term "Cal OSHA drop test" refers to the above
described test.
These results indicate that the rebar protective cover of this
invention is likely to be more effective in preventing serious
puncture injuries to workmen accidentally falling on the end of
exposed rebar.
* * * * *